The invention relates to a gripper mechanism for devices for handling objects in the form of sheets or plates, in particular for post processing machines.
Generally known gripper mechanisms of this type, which have been in use for a long time, contain a gripper arm which can pivot about a gripper arm pivoting shaft and can be moved transversely with respect to the movement direction of a transfer chain, which is driven intermittently for example, by means of an appropriate drive, for example a crank drive, to carry out reciprocating pivoting movements. At its free end, the gripper arm is fitted with a gripper hand which has a pair of interacting gripper claws of which, in general, one is designed to be fixed relative to the gripper arm and the other is fitted such that it can pivot relative to the gripper arm. The pivoting gripper claw is moved by means of a claw operating drive against the force of spring means, which hold the gripper claws in the closed position, in specific pivoting positions of the gripper arm in the open position in order to grip either a specific object in the form of a sheet or plate, or a corresponding stack of such objects, and once the gripper claws have closed, to transport them to the transfer chain or else, when this handling process has been completed, to release the relevant object or stack of objects once again so that the compartment on the transfer chain which has now been filled can continue to move with said chain. One known embodiment of a gripper claw operating drive provides an operating lever arrangement which is mounted on the gripper arm such that it can pivot, can be pivoted by means of a claw operating drive apparatus during the pivoting movements of the relevant gripper arm, and is connected via a coupling linkage to the gripper claw which can pivot with play or a clearance which allows a specific opening of the gripper claws against the force of the spring prestressing means regardless of the respective position of the operating lever arrangement. In general, the operating lever arrangements for a plurality of gripper arms which are operated at the same time and are forced to move synchronously in a reciprocating manner are seated on a common operating shaft which is mounted on each of the simultaneously moved gripper arms, and is rotated in a reciprocating manner in specific gripper arm pivoting positions via a slotted guide link, a slotted guide link feeler and a feeler roll lever, which is firmly attached to the operating shaft, in order to operate the respective pivoting gripper claws on the individual gripper arms simultaneously, so that the operating lever arrangements which are seated on the operating shaft move the moving gripper claws to the open position via the individual coupling linkage.
For certain post processing tasks, it is necessary to make up a despatch from enclosures which consist of a sheet or a small number of sheets, and possibly folded sheets, and enclosures which consist of a stack of bound or stapled sheets. In this case, difficulties arise in setting gripper mechanisms of the same type and at processing stations arranged successively along a transfer chain to enclosures of different thickness such that, on the one hand, thin enclosures can be gripped reliably when being handled and a monitoring device provided on the respective gripper mechanism responds correctly in order to record multiple outputs or empty outputs and, on the other hand, when handling thick enclosures, to ensure that the clamping forces during handling are sufficient for the relevant gripper mechanism to apply the required forces when drawing the enclosure from the stack and to introduce the necessary acceleration forces to the enclosure, without losing it. The setting effort required to do this is in some cases high with known gripper mechanisms.
The invention is thus intended to achieve the object of refining a gripper mechanism having the features of the precharacterizing clause of claim 1 such that it can be set easily and reliably to handle both light, thin objects and thick, heavy objects.
According to the invention, this object is achieved by the characterizing features of claim 1. Advantageous refinements and developments are the subject matter of the claims but are dependent on claim 1, whose content hereby expressly forms part of the description without having to repeat the wording in detail here.
One particular embodiment of the gripper mechanism of the type specified here can be dismantled with a few actions for servicing and repair. The settings made are maintained on the gripper mechanism under the influence of reaction forces in operation even if adjustable parts on the gripper mechanism are fixed with comparatively low clamping forces.